/**
 * Hightly based on: "Using Sass to automatically pick text colors"
 * https://medium.com/dev-channel/using-sass-to-automatically-pick-text-colors-4ba7645d2796
 */

/**
 * Precomputed linear color channel values, for use in contrast calculations.
 * See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
 * ---
 *
 *  Algorithm, for c in 0 to 255:
 *  f(c) {
 *    c = c / 255;
 *    return c < 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
 *  }
 *
 *  This lookup table is needed since there is no `pow` in SASS.
 *
 * ---
 * @access private
 * @type Map
 * @group themes
 */

$md-linear-channel-values:
  0
  .0003035269835488375
  .000607053967097675
  .0009105809506465125
  .00121410793419535
  .0015176349177441874
  .001821161901293025
  .0021246888848418626
  .0024282158683907
  .0027317428519395373
  .003035269835488375
  .003346535763899161
  .003676507324047436
  .004024717018496307
  .004391442037410293
  .004776953480693729
  .005181516702338386
  .005605391624202723
  .006048833022857054
  .006512090792594475
  .006995410187265387
  .007499032043226175
  .008023192985384994
  .008568125618069307
  .009134058702220787
  .00972121732023785
  .010329823029626936
  .010960094006488246
  .011612245179743885
  .012286488356915872
  .012983032342173012
  .013702083047289686
  .014443843596092545
  .01520851442291271
  .01599629336550963
  .016807375752887384
  .017641954488384078
  .018500220128379697
  .019382360956935723
  .0202885630566524
  .021219010376003555
  .022173884793387385
  .02315336617811041
  .024157632448504756
  .02518685962736163
  .026241221894849898
  .027320891639074894
  .028426039504420793
  .0295568344378088
  .030713443732993635
  .03189603307301153
  .033104766570885055
  .03433980680868217
  .03560131487502034
  .03688945040110004
  .0382043715953465
  .03954623527673284
  .04091519690685319
  .042311410620809675
  .043735029256973465
  .04518620438567554
  .046665086336880095
  .04817182422688942
  .04970656598412723
  .05126945837404324
  .052860647023180246
  .05448027644244237
  .05612849004960009
  .05780543019106723
  .0595112381629812
  .06124605423161761
  .06301001765316767
  .06480326669290577
  .06662593864377289
  .06847816984440017
  .07036009569659588
  .07227185068231748
  .07421356838014963
  .07618538148130785
  .07818742180518633
  .08021982031446832
  .0822827071298148
  .08437621154414882
  .08650046203654976
  .08865558628577294
  .09084171118340768
  .09305896284668745
  .0953074666309647
  .09758734714186246
  .09989872824711389
  .10224173308810132
  .10461648409110419
  .10702310297826761
  .10946171077829933
  .1119324278369056
  .11443537382697373
  .11697066775851084
  .11953842798834562
  .12213877222960187
  .12477181756095049
  .12743768043564743
  .1301364766903643
  .13286832155381798
  .13563332965520566
  .13843161503245183
  .14126329114027164
  .14412847085805777
  .14702726649759498
  .14995978981060856
  .15292615199615017
  .1559264637078274
  .1589608350608804
  .162029375639111
  .1651321945016676
  .16826940018969075
  .1714411007328226
  .17464740365558504
  .17788841598362912
  .18116424424986022
  .184474994500441
  .18782077230067787
  .19120168274079138
  .1946178304415758
  .19806931955994886
  .20155625379439707
  .20507873639031693
  .20863687014525575
  .21223075741405523
  .21586050011389926
  .2195261997292692
  .2232279573168085
  .22696587351009836
  .23074004852434915
  .23455058216100522
  .238397573812271
  .24228112246555486
  .24620132670783548
  .25015828472995344
  .25415209433082675
  .2581828529215958
  .26225065752969623
  .26635560480286247
  .2704977910130658
  .27467731206038465
  .2788942634768104
  .2831487404299921
  .2874408377269175
  .29177064981753587
  .2961382707983211
  .3005437944157765
  .3049873140698863
  .30946892281750854
  .31398871337571754
  .31854677812509186
  .32314320911295075
  .3277780980565422
  .33245153634617935
  .33716361504833037
  .3419144249086609
  .3467040563550296
  .35153259950043936
  .3564001441459435
  .3613067797835095
  .3662525955988395
  .3712376804741491
  .3762621229909065
  .38132601143253014
  .386429433787049
  .39157247774972326
  .39675523072562685
  .4019777798321958
  .4072402119017367
  .41254261348390375
  .4178850708481375
  .4232676699860717
  .4286904966139066
  .43415363617474895
  .4396571738409188
  .44520119451622786
  .45078578283822346
  .45641102318040466
  .4620769996544071
  .467783796112159
  .47353149614800955
  .4793201831008268
  .4851499400560704
  .4910208498478356
  .4969329950608704
  .5028864580325687
  .5088813208549338
  .5149176653765214
  .5209955732043543
  .5271151257058131
  .5332764040105052
  .5394794890121072
  .5457244613701866
  .5520114015120001
  .5583403896342679
  .5647115057049292
  .5711248294648731
  .5775804404296506
  .5840784178911641
  .5906188409193369
  .5972017883637634
  .6038273388553378
  .6104955708078648
  .6172065624196511
  .6239603916750761
  .6307571363461468
  .6375968739940326
  .6444796819705821
  .6514056374198242
  .6583748172794485
  .665387298282272
  .6724431569576875
  .6795424696330938
  .6866853124353135
  .6938717612919899
  .7011018919329731
  .7083757798916868
  .7156935005064807
  .7230551289219693
  .7304607400903537
  .7379104087727308
  .7454042095403874
  .7529422167760779
  .7605245046752924
  .768151147247507
  .7758222183174236
  .7835377915261935
  .7912979403326302
  .799102738014409
  .8069522576692516
  .8148465722161012
  .8227857543962835
  .8307698767746546
  .83879901174074
  .846873231509858
  .8549926081242338
  .8631572134541023
  .8713671191987972
  .8796223968878317
  .8879231178819663
  .8962693533742664
  .9046611743911496
  .9130986517934192
  .9215818562772946
  .9301108583754237
  .938685728457888
  .9473065367331999
  .9559733532492861
  .9646862478944651
  .9734452903984125
  .9822505503331171
  .9911020971138298
  1;


/**
 * Calculate the luminance for a color.
 * ---
 * @access private
 * ---
 * @param {string} $color —  The color to be analysed
 */

@function md-check-luminance($color) {
  $red: nth($md-linear-channel-values, red($color) + 1);
  $green: nth($md-linear-channel-values, green($color) + 1);
  $blue: nth($md-linear-channel-values, blue($color) + 1);

  @return .2126 * $red + .7152 * $green + .0722 * $blue;
}


/**
 * Calculate the contrast ratio between two colors.
 * ---
 * @access private
 * ---
 * @param {string} $bg —  The bg color
 * @param {string} $fg —  The fg color to be compared
 */

@function md-calculate-contrast($bg, $fg) {
  $bgLum: md-check-luminance($bg) + .2;
  $fgLum: md-check-luminance($fg) + .2;

  @return max($bgLum, $fgLum) / min($bgLum, $fgLum);
}


/**
 * Determine whether to use dark or light text on top of given color.
 * Returns dark or light depending on the contrast ratio.
 * ---
 * @access private
 * ---
 * @param {string} $color —  The desired color to be compared
 */

@function md-pick-contrast($color) {
  $lightColor: map-get(map-get($md-color-levels, dark), text-primary);
  $lightContrast: md-calculate-contrast($color, $lightColor);
  $darkColor: map-get(map-get($md-color-levels, light), text-primary);
  $darkContrast: md-calculate-contrast($color, $darkColor);

  @if ($lightContrast > $darkContrast) {
    @return "dark";
  }

  @return "light";
}
